Molds are commonly used tools used to convert a material into a given shape; the shaped material is referred to as a molded object. Examples of desired materials used for molds are elastomers, plastics, and resins. Examples of common elastomers are urethanes, natural rubber, butyl rubber, ethylene acrylic, and neoprene. Once injected into the mold, the elastomer or other material takes the shape of the mold. Molded objects often adhere tightly to the molds during this shaping process. To allow the molded object to be removed from the mold with low force and without damage to the molded object, the mold is typically coated with a release agent.
There are three main categories of release agents: sacrificial, semi-permanent, and permanent. Sacrificial release agents typically need to be applied to a mold every time a mold is used. Examples of sacrificial mold release agents include waxes, fatty acid or esters, and silicone oils. Semi-permanent release agents provide multiple releases per application. Semi-permanent release agents are typically particulate fluorocarbon materials or cured films of siloxanes. Both sacrificial and semi-permanent release agents are typically applied and repaired by a person doing the molding, commonly referred to as the “molder”. Permanent release agents last longer than semi-permanent release agents and are generally a coating on the mold of a fluorocarbon polymer which is melted and applied to the mold at high temperature. Permanent release agents are applied to the mold by an outside company (company other than the molder) who has special equipment to generate the required temperatures to melt the fluoropolymer coatings. When damaged, permanent release agent coatings generally cannot be repaired by the molder. The molder must send the mold with the damaged coating to the outside company to repair the coating.
Release agents that allow the production of multiple molded objects before they must be reapplied to a mold, are desirable to increase production and decrease build-up of release agent within the mold. Release agents should also provide easy release of the molded object to avoid damage to the object as the object is removed from the mold, that is, during the “de-molding process”.
Stephens discloses compositions, which allow several releases before recoating, but have relatively long lists of components. In U.S. Pat. No. 5,298,556, Stephens discloses a mold release agent comprising (1) a silane, (2) a multifunctional polydimethyl siloxane emulsified polymer, (3) a substituted nonyl or octyl phenol derivative surfactant, (4) a non-ionic surfactant, (5) a synthetic ethoxylated amine surfactant, (6) a silanol-terminated polydimethyl siloxane, (7) a low molecular weight alcohol, (8) a weak acid to maintain a pH 4.5 to 5.5, and (9) water. In U.S. Pat. No. 5,601,641, Stephens discloses a mold release agent comprising (1) a silane, (2) a methyl-terminated polydimethylsiloxane emulsified polymer, (3) a non-ionic surfactant, (4) a silanol-terminated polydimethylsiloxane, (5) a low molecular weight alcohol, (6) a fungicide, (7) a metallic salt or an organic acid, (8) a weak acid to maintain a pH 4.5 to 5.5, (9) a hydroxyl-terminated polybutadiene, and (10) water.
In U.S. Pat. No. 6,596,829, Peavy describes a release agent based upon a low molecular weight fluorotelomer that contains functional endgroups for improved bonding to the surface of a mold. The composition is crosslinked with a catalyst to form a film on a substrate. The release agent is capable of multiple releases before reapplication is needed.
Still, there remains a need for a release agent composition which allows for a greater number of releases and that can be easily applied or repaired by the molder without the need for complicated synthesis, or the use of complicated machinery, or extended down production time. The release agent should allow for multiple molding operations and low force to remove the molded object. The present invention meets these needs.